[PATCH AUTOSEL 6.14 352/642] rtnetlink: Lookup device in target netns when creating link

Sasha Levin
2025-05-05T22:28:24Z

From: Xiao Liang <shaw.leon@gmail.com>

[ Upstream commit ec061546c6cffbb8929495bba3953f0cc5e177fa ]

When creating link, lookup for existing device in target net namespace
instead of current one.
For example, two links created by:

# ip link add dummy1 type dummy
# ip link add netns ns1 dummy1 type dummy

should have no conflict since they are in different namespaces.

Signed-off-by: Xiao Liang <shaw.leon@gmail.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250219125039.18024-2-shaw.leon@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/core/rtnetlink.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 80e006940f51a..ab7041150f295 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -3865,20 +3865,26 @@ static int __rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
{
struct nlattr ** const tb = tbs->tb;
struct net *net = sock_net(skb->sk);
+ struct net *device_net;
struct net_device *dev;
struct ifinfomsg *ifm;
bool link_specified;

+ /* When creating, lookup for existing device in target net namespace */
+ device_net = (nlh->nlmsg_flags & NLM_F_CREATE) &&
+ (nlh->nlmsg_flags & NLM_F_EXCL) ?
+ tgt_net : net;
+
ifm = nlmsg_data(nlh);
if (ifm->ifi_index > 0) {
link_specified = true;
- dev = __dev_get_by_index(net, ifm->ifi_index);
+ dev = __dev_get_by_index(device_net, ifm->ifi_index);
} else if (ifm->ifi_index < 0) {
NL_SET_ERR_MSG(extack, "ifindex can't be negative");
return -EINVAL;
} else if (tb[IFLA_IFNAME] || tb[IFLA_ALT_IFNAME]) {
link_specified = true;
- dev = rtnl_dev_get(net, tb);
+ dev = rtnl_dev_get(device_net, tb);
} else {
link_specified = false;
dev = NULL;
--
2.39.5